A related conventional rotation device is disclosed in Japanese Laid-Open Utility Model Publication No. 2000-53381 (Japanese Patent No. 3338952).
The rotation device disclosed in Japanese Laid-Open Utility Model Publication No. 2000-53381 a winch, which has a main drum and a sub drum that are positioned coaxially. The main drum is connected to a main hydraulic motor via a main gear mechanism. Conversely, the sub drum is connected to a sub hydraulic motor via a sub gear mechanism. That is, each of the drums can be driven by a motor and a gear mechanism.
To the contrary, in order to downsize a mechanism for driving the drum, a drum may be driven by using two small motors and two sets of gear mechanisms (dram-side gears and motor-side gears). In this case, upon actuation of the two motors in synchrony with each other, similar to the case in which a single motor is used, the drum can be rotated in a winding direction or an unwinding direction. The drum, the gear mechanisms and the motors are attached to predetermined positions of a bracket (not shown).